Ball Game Touch Counter

Ball Game Touch Counter reads a comma-separated visibility file and prints the maximum number of players who can touch the ball. A player can pass the ball only through mutual visibility: if A lists B, B must also list A.

Input Format

Each non-blank line starts with a player, followed by the players they can see:

George,Beth,Sue
Rick,Anne
Anne,Beth
Beth,Anne,George
Sue,Beth

Rules:

• Names are trimmed for surrounding whitespace.
• Blank lines are ignored.
• Empty names are invalid.
• Names may contain special or Unicode characters.
• Names containing commas must use CSV quoting, such as "George, Jr.",Beth.
• A name can be at most 20 characters.

Run

Requires Go 1.19 or newer.

go run . -file /path/to/players.txt

Build a binary:

go build -o ballgame
./ballgame -file /path/to/players.txt

Test

go test ./...

Project Structure

main.go              wires the CLI handler, service, and file reader
pkg/handler          command-line boundary: flags, stdout/stderr, exit codes
pkg/service          orchestration: read player data, build graph, calculate result
pkg/file             file-backed data access
pkg/game             domain logic: graph building and mutual-visibility traversal

Algorithm

The app builds an adjacency list from the input file, then finds the largest connected component using only reciprocal edges. For example, A -> B counts only when B -> A also exists.

MaxTouches visits each graph component once, so the calculation is linear in the number of players plus visibility entries.